An overedge sewing machine for cutting the edge of a fabric while sewing an overedge stitch

Description

[0001] This invention relates to an overedge sewing machine for cutting the edge of a fabric and sewing an overedge stitch at the same time.

[0002] U.S. Patent No. 4570558 discloses one known overedge sewing machine. In this prior-art overedge sewing machine, a lower knife holder supporting a lower knife may move perpendicular the fabric-feed direction. When an adjustment knob is rotated, an external screw is engaged with an internal screw, the lower knife holder is moved, and stitch width is thus adjusted. A stitch-support member is fixed on the lower knife holder. When the stitch width is altered, the stitch-support member is moved together with the lower knife holder.

[0003] Generally, an excess amount of upper and lower looper thread is necessary for the thread to reciprocate between the needle location and the fabric edge. Excess thread in proportion to the stitch width is also necessary. In this prior art, an adequate amount of reciprocating thread corresponding to the stitch width can be obtained. However, since the stitch-support member moves together with the lower knife and the relative position of the stitch-support member with the lower knife does not change, an adequate amount of excess thread proportional to the stitch width cannot be obtained. The amount of thread is so insufficient that the stitch becomes too taut when the adjusted stitch width increases.

[0004] Another known overedge sewing machine is disclosed in U.S. Patent No. 4690079. In this prior-art overedge sewing machine, the lower knife holder supporting the lower knife may move perpendicular to the cloth feed direction. When the adjustment knob is rotated, a movable member is moved and the external screw is engaged with the internal screw. The lower knife holder is moved accordingly, and the stitch width is thus adjusted. The stitch-support member attached to the movable member crosses the fabric-feed direction at a right angle. After the stitch width is adjusted, the position of the stitch-support member can be finely adjusted by loosening a set screw.

[0005] In this prior art, when the stitch width is altered, the position of the lower knife holder should be adjusted, then that of the stitch-support member should be finely adjusted. On the other hand, the movable member of the lower knife holder supports the stitch-support member, so the stitch-support member moves together with the lower knife holder when the stitch width is altered. Every time the stitch width is adjusted, the position of the stitch-support member must be finely adjusted according to the type of the fabric.

[0006] One aim of the invention is, therefore, to provide an overedge sewing machine where, by securing an adequate excess thread proportional to an adjusted stitch width, a stitch can be steadily formed regardless of the stitch width without increasing the tension in the threads.

[0007] Another aim of the invention is to provide an overedge sewing machine where the position of the lower knife holder supporting the lower knife and that of the stitch-support member can be adjusted easily using one adjustment member.

[0008] According to the present invention there is provided an overedge sewing machine comprising:
   upper and lower knives disposed on the feed side in the front of a needle location for cutting an edge of a fabric being fed toward the needle location;
   a lower knife holder movable in a direction perpendicular to the fabric-feed direction for supporting the lower knife;
   a stitch-support member near the needle location, extending away from the feed side and movable in the direction perpendicular to the fabric-feed direction; and
   an adjustment member for adjusting the stitch width; characterised in that it further comprises:
   displacement means responsive to said adjustment member and adapted to move said lower knife holder and said stitch-support member by respective amounts on movement of said adjustment member, said respective amounts being different from each other for some or all movements of said adjustment member.

[0009] The invention will be further explained hereafter with reference to the following description of preferred exemplary embodiments of the present invention and the accompanying drawings in which:

Fig. 1 is a perspective view of an overedge sewing machine of the described embodiments of the invention;

Fig. 2 is a partial front sectional view showing a lower knife holder and a stitch-support member of the embodiments;

Fig. 3A is a side sectional view of Fig. 2 of the first embodiment;

Fig. 3B is a side sectional view of Fig. 2 of the second embodiment;

Fig. 4 is a partial top view of Fig. 2;

Fig. 5 illustrates stitch formation at the edge of the fabric;

Fig. 6 is a graph showing the displacement of cam members in the first embodiment; and

Fig. 7 is a graph showing the displacement of cam members in the second embodiment.

[0010] Embodiments of the present invention will be described referring to the drawings.

[0011] As shown in Fig. 1, a sewing machine body 1 comprises an arm 2 and a bed 3. The arm 2 has a needle bar 4. A needle 5 attached to the lower edge of the needle bar 4 sews an overedge stitch S on the edge of fabric W in cooperation with a known looper provided in the bed 3. An upper knife 6 is movably attached on the operator's side in front of a needle location in the bed 3. The upper knife 6 and a lower knife 7 fixed to the bed 3 cooperate to cut the edge of the fabric W being fed toward the needle location before overedge stitch is sewed.

[0012] The structure for supporting and adjusting the lower knife 7 is now explained. As shown in Fig. 2, a lower knife holder 8 is movably attached through a pair of support pins 9 to the bed 3, and can move perpendicular to the fabric-feed direction . The lower knife 7 is fixed with a screw 10 to the right side of the lower knife holder 8. Compression springs 11 are inserted between the bed 3 and spring washers 12 fixed at the tips of the pins 9. The resilience of the compression spring 11 moves the lower knife holder 8 to the left in Fig. 2.

[0013] A needle plate 13 is fixed on the top of the bed 3 of the sewing machine body 1. As shown in Fig. 4, a stationary stitch-support member 14 is fixed near the needle location extending away from the operator. As shown in Figs. 2 and 3A, a movable member 15 is adjacent to the lower knife holder 8. The movable member 15 is attached through a pair of support pins 16 to the bed 3, and can cross the fabric-feed direction at a right angle. A movable stitch-support tongue 17 is attached to the top of the movable member 15 near the needle location in the fabric-feed direction. As shown in Fig. 5, the movable stitch-support tongue 17 and the stationary stitch-support member 14 temporarily hold the overedge stitch S between each other. Compression springs 18 are inserted between the bed 3 and spring washers 19 provided at the tips of the pins 16. The resilience of the springs 18 moves the movable member 15 to the left in Fig. 2.

[0014] An adjustment member 20 for adjusting stitch width is rotatably attached through a shaft 21 to the bed 3 of the sewing machine body 1. On the periphery of the adjustment member 20, graduation marks 22 marking the stitch width are provided. First and second cam members 23 and 24 are respectively incorporated into each side of the adjustment member 20. The first cam member 23 comprises a horizontal-movement-producing cam and the second cam member 24 comprises a vertical-movement-producing cam. As shown in Fig. 6, in this embodiment, the displacement due to the second cam member 24 is greater than that due to the first cam member 23.

[0015] As shown in Fig. 2, a first transmission lever 25 is rotatably attached through a shaft 26 to the bed 3. One end of the first transmission lever 25 engages the first cam member 23, and the other end engages a support pin 9 supporting the lower knife holder 8. A second transmission lever 27 is rotatably attached through a shaft 28 to the bed 3. One end of the second transmission lever 27 engages the second cam member 24, and the other end engages a pin 16 supporting the movable member 15. The first and second transmission levers 25 and 27 compose a transmission means for individually moving the lower knife holder 8 and the movable member 15 of the stitch-support tongue 17 based on the displacements due to the first and second cam members 23 and 24, respectively.

[0016] In this embodiment, when the adjustment member 20 is rotated according to the graduation marks 22 indicating stitch width, the first cam member 23 operates the first transmission lever 25 causing the lower knife holder 8 supporting the lower knife 7 to cross the fabric-feed direction at a right angle. At the same time, the second cam member 24 operates the second transmission lever 27 causing the movable member 15 with the stitch-support tongue 17 to move in the same direction as the lower knife holder 8. The upper knife 6 is also moved so that it continues to cooperate with the lower knife so as to cut the fabric. The stitch width is thus adjusted. As shown in Fig. 6, the second cam member 24 is displaced more than the first cam member 23. When the stitch width changes, the stitch-support tongue 17 moves more than the lower knife holder 8.

[0017] While the upper knife 6 cuts the edge of the fabric W in cooperation with the lower knife 7, the needle 5 sews the overedge stitch S in cooperation with the known looper. As shown in Fig. 5, the overedge stitch S is temporarily held by and between the stitch-support member 14 and the stitch-support tongue 17. When the stitch width is adjusted by rotating the adjustment member 20, the stitch-support tongue 17 moves more than the lower knife holder 8, so the stitch-support tongue 17 moves apart from the stationary stitch-support member 14. An amount A of thread reciprocating the width of the stitch and an excess amount B of thread both increase. By adjusting only the adjustment member 20, the overedge stitch steadily forms without excessive tension in the thread.

[0018] Another embodiment of the present invention will be explained with reference to the drawings. A second embodiment has the same construction as the first embodiment as shown in Figs. 1, 2, and 4. However, the configuration of the second cam member 24 in the second embodiment in Fig. 3B differs from that in the first embodiment in Fig. 3A.

[0019] In the second embodiment, as shown in Fig. 7, the first cam member 23 has a continuous displacement. The second cam member 24 is displaced by almost the same amount as the first cam member 23, but its displacements are discrete.

[0020] In operation, while the upper knife 6 cuts the edge of the fabric W in cooperation with the lower knife 7, the needle 5 sews the overedge stitch S in cooperation with the known looper. When the adjustment member 20 is rotated, the first and second cam members 23 and 24 operate the first and second transmission levers 25 and 27, and the lower knife holder 8 and the movable member 15 move at right angles to, the fabric-feed direction by almost the same amount. The stitch width is thus adjusted. When the edge of the fabric W is cut and overedge stitch S is sewn, the fabric W, held by a known presser foot assembly, stretches toward the lower knife 7. When the fabric W is released from the presser foot assembly, the fabric W contracts to regain its original length. The expansion and contraction coefficient of the fabric W varies widely with the type of the fabric W. To adjust the stitch width, the relative position between the lower knife 7 and the stitch-support tongue 17 should be finely adjusted according to the type of the fabric W.

[0021] In the second embodiment, after the adjustment member 20 is rotated according to the graduation marks 22 for the stitch width, the adjustment member 20 is finely rotated within a graduation. Then, the first cam member 23 moves the lower knife holder 8 slightly within a graduation in the direction crossing the fabric-feed direction perpendicularly. However, since the second cam member 24 is in phase with a graduation on the adjustment member 20, the movable member 15 having the stitch-support tongue 17 does not move when a fine adjustment is made within a graduation. Consequently, the relative positions of the lower knife 7 and the stitch-support tongue 17 can be adjusted precisely and easily according to the type of the fabric.

[0022] These are only two possible embodiments of the invention claimed below. These embodiments are only illustrations of the claims, and in no way restrict the scope of the claims.

[0023] For instance, the cam members could be provided separately from the adjustment member. The cam members could be operated via a drive shaft by the adjustment member. One cam member could move both the lower knife holder and the stitch-support member individually by different amounts by means of the transmission levers with different lever lengths.

[0024] Furthermore, the first cam member could be displaced discretely, and the second cam member can be displaced continuously.

Claims

1. An overedge sewing machine comprising:
   upper and lower knives (6, 7) disposed on the feed side in the front of a needle location for cutting an edge of a fabric (W) being fed toward the needle location;
   a lower knife holder (8) movable in a direction perpendicular to the fabric-feed direction for supporting the lower knife (7);
   a stitch-support member (17) near the needle location, extending away from the feed side and movable in the direction perpendicular to the fabric-feed direction; and
   an adjustment member (20) for adjusting the stitch width; characterised in that it further comprises:
   displacement means (23-27) responsive to said adjustment member (20) and adapted to move said lower knife holder (8) and said stitch-support member (17) by respective amounts on movement of said adjustment member, said respective amounts being different from each other for some or all movements of said adjustment member.

2. A sewing machine according to claim 1 wherein in use continuous motion of said adjustment member causes continuous displacement of said lower knife holder (8) and said stitch-support member (17) by different amounts.

3. A sewing machine according to claim 1 wherein in use continuous motion of said adjustment member causes continuous displacement of said lower knife holder and stepwise displacement of said stitch support member.

4. A sewing machine according to claim 3 wherein, for movements of said adjustment member corresponding to the width of the steps of said stepwise displacement, said lower knife holder and stitch support member are displaced by equal amounts.

5. A sewing machine according to claim 1, 2 or 3, wherein a given displacement of said adjustment means causes greater displacement of said stitch support member than of said lower knife holder.

6. A sewing machine according to any preceding claim wherein said displacement means comprises cam means.

7. A sewing machine according to claim 6 wherein said can means comprise first and second cam members (23, 24) and transmission means (25, 27) bearing on said cam members for respectively moving said lower knife holder (8) and said stitch support member (17) upon displacement of said adjustment member (20).

8. A sewing machine according to claim 7, in which the adjustment member (20) has a first surface, the first cam member (23) being an inclined surface thereof, and a second surface, the second cam member (24) being an eccentric channel therein.

9. A sewing machine according to claim 8, in which said second cam member (24), is a stepped inner peripheral surface of said eccentric channel so that the relative position between the lower knife (7) and the stitch-support member (17) can be adjusted.

10. An overedge sewing machine according to any one of claims 7 to 9, in which the transmission means (25, 27) comprises:
   a first transmission lever (25) rotatably attached through a shaft (26) to the bed (3), one end of said first transmission lever engaging the first cam member (23), and the other end engaging with a first support pin (9) supporting the lower knife holder (8); and
   a second transmission lever (27) rotatably attached through a shaft (28) to the bed (3), one end of the second transmission lever engaging the second cam member (24), and the other end engaging a second support pin (16) supporting a movable member (15), which moves the stitch-support member (17).

11. A sewing machine according to any preceding claim, in which the adjustment member (20) is rotatably attached through a shaft (21) to a bed (3).

12. An overedge sewing machine according to any preceding claim, in which the periphery of the adjustment member (20) bears graduation marks (22) indicating the stitch width.

Ansprüche

1. Überwendlingnähmaschine mit:
einem oberen und einem unteren Messer (6, 7), die auf der Vorschubseite vor einem Nadelort zum Schneiden einer Kante eines Nähgutes (W) vorgesehen sind, das zu dem Nadelort vorgeschoben wird;
einem unterem Messerhalter (8), der in eine Richtung senkrecht zu der Nähgutvorschubrichtung zum Tragen des unteren Messers (7) bewegbar ist;
einem Stichunterstützungsteil (17) nahe dem Nadelort, das sich von der Vorschubseite wegerstreckt und die Richtung senkrecht zu der Nähgutvorschubrichtung bewegbar ist; und
einem Einstellteil (20) zum Einstellen der Stichbreite;
gekennzeichnet durch:
Verschiebungsmittel (23 - 27), das auf das Einstellteil (20) reagiert und zum Bewegen des unteren Messerhalters (8) und des Stichunterstützungsteiles (17) um entsprechende Beträge auf die Bewegung des Einstellteiles ausgelegt ist, wobei sich die entsprechenden Beträge voneinander für einige oder alle Bewegungen des Einstellteiles unterscheiden.

2. Nähmaschine nach Anspruch 1, bei der in Benutzung eine kontinuierliche Bewegung des Einstellteiles eine kontinuierliche Verschiebung des unteren Messerhalters (8) und des Stichunterstützungsteiles (7) um unterschiedliche Beträge bewirkt.

3. Nähmaschine nach Anspruch 1, bei der in Benutzung eine kontinuierliche Bewegung des Einstellteiles eine kontinuierliche Verschiebung des unteren Messerhalters und eine schrittweise Verschiebung des Stichunterstützungsteiles bewirkt.

4. Nähmaschine nach Anspruch 3, bei der für Bewegungen des Einstellteiles entsprechend der Weite der Schritte der schrittweisen Verschiebung der untere Messerhalter und das Stichunterstützungsteil um gleiche Beträge verschoben werden.

5. Nähmaschine nach Anspruch 1, 2 oder 3, bei der eine gegebene Verschiebung des Einstellteiles eine größere Verschiebung des Stichunterstützungsteiles als die des unteren Messerhalters bewirkt.

6. Nähmaschine nach einem der vorhergehenden Ansprüche, bei der das Verschiebungsmittel Nockenmittel aufweist.

7. Nähmaschine nach Anspruch 6, bei der die Nockenmittel ein erstes und ein zweites Nockenteil (23, 24) und Übertragungsmittel (25, 27) aufweist, die auf den Nockenteilen zum entsprechenden Bewegen des unteren Messerhalters (8) und des Stichunterstützungsteiles (17) auf die Verschiebung des Einstellteiles (20) aufliegen.

8. Nähmaschine nach Anspruch 7, bei der das Einstellteil (20) eine erste Oberfläche, wobei das erste Nockenteil (23) eine geneigte Oberfläche davon ist, und eine zweite Oberfläche, wobei das zweite Nockenteil (24) ein exzentrischer Kanal darin ist, aufweist.

9. Nähmaschine nach Anspruch 8, bei der das zweite Nockenteil (24) eine gestufte innere Umfangsoberfläche des exzentrischen Kanales so ist, daß die Relativposition zwischen dem unteren Messer (7) und dem Stichunterstützungsteil (17) eingestellt werden kann.

10. Überwendlingsnähmaschine nach einem der Ansprüche 7 bis 9, bei der das Übertragungsmittel (25, 27) aufweist:
einen ersten Übertragungshebel (25), der drehbar durch eine Welle (26) an dem Bett angebracht ist, wobei ein Ende des ersten Übertragungshebels in Eingriff mit dem ersten Nockenteil (23) steht und das andere Ende mit einem ersten Trägerstift (9) steht, der den unteren Messerhalter (8) trägt; und
einen zweiten Übertragungshebel (27), der drehbar durch eine Welle (28) an dem Bett (3) angebracht ist, wobei ein Ende des zweiten Übertragungshebel in Eingriff mit dem zweiten Nockenteil (24) steht und das andere Ende mit einem zweiten Trägerstift (16) in Eingriff steht, der ein bewegbares Teil (15) trägt, das das Stichunterstützungsteil (17) bewegt.

11. Nähmaschine nach einem der vorhergehenden Ansprüche, bei der das Einstellteil (29) drehbar durch eine Welle (21) an einem Bett (3) angebracht ist.

12. Überwendlingnähmaschine nach einem der vorhergehenden Ansprüche, bei der der Umfang des Einstellsteiles (20) Unterteilungsmarkierungen (22) trägt, die die Stichbreite anzeigen.

Revendications

1. Machine de surjetage comprenant :

- des lames supérieure et inférieure (6, 7) placées sur le côté d'avance à l'avant d'une position d'aiguille pour la découpe d'un bord d'un tissu (W) avançant vers la position d'aiguille;

- un porte-lame inférieur (8) mobile dans une direction normale à la direction d'avance du tissu pour supporter la lame inférieure (7);

- une pièce de support de couture (17) proche du point d'aiguille, s'étendant à l'écart du côté d'avance et mobile dans la direction normale à la direction d'avance du tissu; et

- une pièce de réglage (20) de la largeur du surjetage;

   machine caractérisée en ce qu'elle comprend de plus :

- des moyens de déplacement (23 à 27) sensibles à ladite pièce de réglage (20) et prévus pour déplacer ledit porte-lame inférieur (8) et ladite pièce de support de couture (17) de quantités respectives lors d'un déplacement de ladite pièce de réglage, lesdites quantités respectives étant différentes l'une de l'autre pour certains ou pour tous les déplacements de ladite pièce de réglage.

2. Machine à coudre selon la revendication 1, dans laquelle, en utilisation, un déplacement en continu de ladite pièce de réglage provoque un déplacement en continu dudit porte-lame inférieur (8) et de ladite pièce de support de couture (17) de quantités différentes.

3. Machine à coudre selon la revendication 1, dans laquelle, en utilisation, un déplacement en continu de ladite pièce de réglage provoque un déplacement en continu dudit porte-lame inférieur et un déplacement pas-à-pas de ladite pièce de support de couture.

4. Machine à coudre selon la revendication 3, dans laquelle, pour des déplacements de ladite pièce de réglage correspondant à la largeur des pas dudit déplacement pas-à-pas, ledit porte-lame inférieur et ladite pièce de support de couture sont déplacés de quantités égales.

5. Machine à coudre selon la revendication 1, 2 ou 3, dans laquelle un déplacement donné dudit moyen de réglage provoque un déplacement plus grand de ladite pièce de support de couture que dudit porte-lame inférieur.

6. Machine à coudre selon l'une quelconque des revendications précédentes, dans laquelle ledit moyen de déplacement comprend un moyen de came.

7. Machine à coudre selon la revendication 6, dans laquelle ledit moyen de came comprend des première et seconde pièces de came (23, 24) et des moyens de transmission (25, 27) portant sur lesdites pièces de came pour un déplacement respectif dudit porte-lame inférieur (8) et de ladite pièce de support de couture (17) lors d'un déplacement de ladite pièce de réglage (20).

8. Machine à coudre selon la revendication 7, dans laquelle la pièce de réglage (20) possède une première surface, la première pièce de came (23) étant une surface inclinée, et une seconde surface, la seconde pièce de came (24) étant un canal excentré.

9. Machine à coudre selon la revendication 8, dans laquelle ladite seconde pièce de came (24) est une surface périphérique interne étagée dudit canal excentré de telle façon que la position relative entre la lame inférieure (7) et la pièce de support de couture (17) puisse être réglée.

10. Machine de surjetage selon l'une quelconque des revendications 7 à 9, dans laquelle les moyens de transmission (25, 27) comprennent :

- un premier levier de transmission (25) fixé tournant via un arbre (26) au lit (3), une extrémité dudit premier levier de transmission (25) coopérant avec la première pièce de came (23) et l'autre extrémité coopérant avec une première broche de support (9) supportant le porte-lame inférieur (8); et

- un second levier de transmission (27) fixé tournant via un arbre (28) au lit (3), une extrémité du second levier de transmission (27) coopérant avec la seconde pièce de came (24) et l'autre extrémité coopérant avec une seconde broche de support (16) supportant une pièce mobile (15) déplaçant la pièce de support de couture (17).

11. Machine à coudre selon l'une quelconque des revendications précédentes, dans laquelle la pièce de réglage (20) est fixée, de façon tournante, via un arbre (21) à un lit (3).

12. Machine de surjetage selon l'une quelconque des revendications précédentes, dans laquelle la périphérie de la pièce de réglage (20) porte des graduations (22) indiquant la largeur du point.

Drawing